Advances in semi-conductor processing and logic design have permitted an increase in the amount of logic that may be present on integrated circuit devices. As a result, computer system configurations have evolved from a single or multiple integrated circuits in a system to multiple cores, multiple hardware threads, and multiple logical processors present on individual integrated circuits. A processor or integrated circuit typically comprises a single physical processor die, where the processor die may include any number of cores, hardware threads, or logical processors. The ever increasing number of processing elements—cores, hardware threads, and logical processors—on integrated circuits enables more tasks to be accomplished in parallel. However, as logic and the number of processing elements grow, the susceptibility of processors to hard faults also increases.
As a result, hard faults, such as a bit stuck at a specific level, may threaten yield, performance and reliability of processors. Defects detected at the time of manufacture, potentially result in lost sales; either from reduced yield—scrapping a physical processor—or reducing execution capacity—selling a physical processor with less logic, such as fewer cores. Alternatively, a hard fault may develop over time—a wear out defect—resulting in a potential failure of a part already sold and in operation. Here, the fault or defect may cause the processor to become unstable, may reduce the processor's performance, or may result in the complete failure of the part.